In certain fluid-handling systems, it is necessary to maintain a high degree of purity in the serviced fluids (i.e., liquids or gases). To this end, certain hermetically-sealed single-diaphragm valves, such as the "SPD.TM." valve manufactured by Carten Systems, Inc., Middlebury, Conn., have been developed. These valves have a body provided with a flow passageway therethrough. An annular seat surrounds a portion of this passageway. A metal diaphragm assembly is movable toward and away from the seat, and forms a flexible wall portion of the flow passageway.
However, in such systems and or in other systems in which the serviced fluid is toxic or noxious, there is a need to provide a redundant or secondary fluid-containment system which surrounds the primary containment system. Hence, should the primary containment system leak for any reason, the escaping gas will leak into the secondary containment system, and will be prevented from entering the atmosphere.
Such dual-containment systems, while affording the capability of redundant protection against leakage and contamination, present special problems with respect to the design of valves and actuators therefor, for the desired mechanical movement must sealingly penetrate the outer containment system without adversely affecting its fluid-tight sealed integrity.